CN101610166B - An intermediate node, cascade protection system and cascade protection method - Google Patents

Abstract

The embodiment of the invention belongs to the technical field of communication and discloses an intermediate node, a cascade protection system and a cascade protection method. The intermediate node is connected with a first node through a first working channel and a first protection channel, and connected with a second node through a second working channel and a second protection channel. The cascade protection system comprises a receiving unit and a processing unit, wherein the receiving unit is used for receiving and then outputting a first signal of the first working channel and a second signal of the first protection channel, and receiving and then outputting a first monitoring message corresponding to the first signal and a second monitoring message corresponding to the second signal; the processing unit is used for judging whether the first signal and the second signal are normal according to the first monitoring message and the second monitoring message output by the receiving unit; and if the first signal and the second signal are judged to be normal, the first signal is output to the second working channel, and the second signal is output to the second protection channel. The intermediate node, the cascade protection system and the cascade protection method can shorten the switching time of services during a single-point fault.

Description

An intermediate node, cascade protection system and cascade protection method

technical field

The invention relates to the field of network management, in particular to an intermediate node, a cascade protection system and a cascade protection method.

Background technique

Due to man-made or natural reasons, communication optical cables are often blocked. The current fiercely competitive communication market requires communication operators to ensure unimpeded customer communication, and communication services have higher and higher requirements for recovery time after business interruption. SNCP (Sub-network Connection Protection) was developed under this background. SNCP is a dedicated protection mechanism, used to protect the protection class of some paths in one or more operator networks, and can support cascaded protection subnets, which is an important protection type in the transport network.

According to the implementation of SF (Signal Failure, signal failure)/SD (Signal Degrade, signal degradation) defect status monitoring, SNCP can be further divided into three subcategories: SNC/S (SNCP with Sublayer Monitoring, SNCP using sublayer monitoring) , SNC/N (Non-intrusively Monitored Sub-Network Connection Protection, using non-intrusively monitored sub-network connection protection), SNC/I (Inherently Monitored Sub-Network Connection Protection, using inherently monitored sub-network connection protection).

SNC/S detects the defect status of the service layer, the continuity/connectivity defect status in the layer network, and the bit error degradation status in the layer network, through the use of sub-layer overhead/OAM (Operations, Administration and Maintenance, operation, management and maintenance) to achieve monitor. The SNC/N monitoring method is to detect end-to-end or sub-layer overhead or OAM information in the signal. SNCP/I only supports the detection of service layer defects. Using the failure of the service layer, the service layer failure or degradation alarm can be derived from the adaptation function between the subnet connection SNC signal and the service layer that needs to be protected.

The 1+1 SNC/N protection structure configuration in Figure 1 can be used as the source node for protection at any point on the path, or as the sink node for protection at any point on the path. There are two independent subnet connections, showing For working and protection transport entities, used for the transmission of protected normal service signals. The non-intrusive monitoring function monitors the SNC/N end-to-end overhead/OAM information to determine the status of working and protection transport entities.

In Figure 1, an ODUk (ODUk Optical Channel Data Unit, Optical Channel Data Unit) SNC/N monitors the signal from A dual transmission to B selective reception, and from B dual transmission to C selective reception.

During the research and practice of the prior art, the inventor found that the node switching of the prior art cascaded protection system in Fig. 1 has the following problems: for the SNC/N of the first ODUk, its monitoring range is from A to B. For the SNC/N of the second ODUk, its monitoring range is from A to C, so it is possible that a fault may cause multiple switchovers as shown in Figure 2 below.

As shown in Figure 2, in the case of multiple protection connections, Figure 2(a) is the business flow chart when all nodes are normal, and the working channel between the first node and the second node in Figure 2(b) fails , when the second node detects a fault, it will insert an AIS (Alarm Indicator Signal, alarm indicator signal) into the working channel and the protection channel between the second node and the third node while performing the switchover. Before the switchover of the second node is successful, the down-inserted AIS has been delivered to the third node. Due to the difference in the length of the optical fiber, the state of the software and hardware of each node is different, and the order in which faults are detected and processed by each channel of each node may be different. The third working channel may receive AIS before the protection channel. The third node cannot determine which of the two previous nodes is faulty, and will directly trigger switching, switching services from the working channel to the protection channel. Due to the influence of factors such as fiber length and node processing methods, as shown in Figure 2(c), the switching of the third node may be successful before the switching of the second node is successful. Then, as shown in Fig. 2(d), the switching of the second node succeeds. Afterwards, the third node detects that the working channel fails and the AIS disappears, but the protection channel may still be in the AIS state due to the long delay, and it will trigger switching again, as shown in Figure 2(e), and switch the service back to the working aisle. Therefore, one fault triggered three switching operations, which made the switching time longer and could not meet customer needs.

Contents of the invention

In order to increase the stability of the protection system, improve the switching efficiency, and shorten the switching time, the embodiment of the present invention provides an intermediate node, a cascading protection system and a cascading protection method.

On the one hand, the embodiment of the present invention provides an intermediate node, which is connected to the first node through the first working channel and the first protection channel, and connected to the second node through the second working channel and the second protection channel, and the intermediate node include:

a receiving unit, configured to receive the first signal of the first working channel and the second signal of the first protection channel and then output it, and receive the first monitoring information corresponding to the first signal and the first monitoring information corresponding to the second signal output after the second monitoring information;

a processing unit, configured to judge whether the first signal and the second signal are normal according to the first monitoring information and the second monitoring information output by the receiving unit;

If it is judged that both the first signal and the second signal are normal, the first signal is output to the second working channel, and the second signal is output to the second protection channel.

On the one hand, an embodiment of the present invention provides a cascade protection system, including a first node, an intermediate node, and a second node, the intermediate node is connected to the first node through a first working channel and a first protection channel, Connected to the second node through a second working channel and a second protection channel, the intermediate node includes:

The receiving unit is configured to receive the first signal of the first working channel and the second signal of the first protection channel and then output it, and receive the first monitoring information corresponding to the first signal and the second monitoring information corresponding to the second signal post output;

a processing unit, configured to judge whether the first signal and the second signal are normal according to the first monitoring information and the second monitoring information output by the receiving unit;

If it is judged that both the first signal and the second signal are normal, the first signal is output to the second working channel, and the second signal is output to the second protection channel.

On the other hand, the embodiment of the present invention also provides a cascade protection method, which is used in a cascade protection system, and the cascade protection system includes a first node, an intermediate node, and a second node, and the intermediate node passes through the first A working channel and the first protection channel are connected to the first node, and are connected to the second node through the second working channel and the second protection channel, and the method includes:

The intermediate node receives the first signal on the first working channel and the second signal on the first protection channel, and receives first monitoring information corresponding to the first signal and the second signal Corresponding second monitoring information;

judging whether the input first signal and second signal are normal based on the first monitoring information and the second monitoring information,

If all are normal, output the first signal to the second working channel, and output the second signal to the second protection channel.

With the above technical solution, since both the first working channel and the first protection channel are normal, the first signal of the first working channel is transmitted to the working channel of the second node, and the second signal of the first protection channel is transmitted to the second node. The two-node protection channel ensures that after a node detects a fault, it will only send an AIS signal to one of the working channel and the protection channel between the node and the next node while performing the switchover, thereby avoiding the working channel and the protection channel. The channel receives the AIS signal at the same time and the AIS signal of the working channel and the protection channel disappears asynchronously, which may cause repeated switching, which shortens the time for service switching when a single point of failure occurs.

Description of drawings

Figure 1 shows the 1+1 SNC/N protection structure configuration of the prior art;

Fig. 2 is a schematic diagram of node switching caused by multiple switching due to a fault in the prior art 1+1 SNC/N protection structure;

Figure 3 is a structural diagram of a cascaded protection system according to an embodiment of the present invention;

FIG. 4 is a structural diagram of a cascaded protection system according to another embodiment of the present invention;

Fig. 5 is a flow chart of a cascade protection method provided by another embodiment of the present invention;

Detailed ways

Embodiments according to the present invention will be described in detail below with reference to the accompanying drawings.

As shown in Figure 3, an embodiment of the present invention provides a cascaded protection system including the intermediate node provided by the embodiment of the present invention, the cascaded protection system also includes a first node and a second node, and the intermediate node passes through the first A working channel and a first protection channel are connected to the first node, and are connected to the second node through a second working channel and a second protection channel, and the intermediate node includes a receiving unit and a processing unit, wherein:

The receiving unit outputs after receiving the first signal of the first working channel and the second signal of the first protection channel, and outputs after receiving the first monitoring information corresponding to the first signal and the second monitoring information corresponding to the second signal;

The processing unit judges whether the first signal and the second signal are normal according to the first monitoring information and the second monitoring information output by the receiving unit; if it is judged that the first signal and the second signal are normal, output the first signal to the second The working channel outputs the second signal to the second protection channel.

Since both the first working channel and the first protection channel are normal, the first signal of the first working channel is transmitted to the working channel of the second node, and the second signal of the first protection channel is transmitted to the protection channel of the second node , to ensure that after a node detects a fault, it will only send an AIS signal to one of the working channel and the protection channel between the node and the next node while performing the switchover, thereby preventing the working channel and the protection channel from receiving AIS at the same time The signal and the AIS signal of the working channel and the protection channel are asynchronously lost, which may cause repeated switching, which shortens the time for switching from the service when a single point of failure occurs.

In another embodiment of the present invention, the difference from the above embodiment shown in FIG. 3 is that the processing unit is configured to: judge the first signal and the second monitoring information according to the first monitoring information and the second monitoring information output by the receiving unit. Whether the signal is normal; if it is judged that both the first signal and the second signal are normal, the first signal is output to the second working channel, and the second signal is output to the second protection channel. If it is judged that the first signal is normal and the second signal is faulty, output the first signal to the second working channel and the second protection channel; if it is judged that the second signal is normal but the first signal is faulty, output the second signal to the second working channel and second protection channel.

Since both the first working channel and the first protection channel are normal, the first signal of the first working channel is transmitted to the working channel of the second node, and the second signal of the first protection channel is transmitted to the protection channel of the second node channel, which ensures that when one of the first working channel and the first protection channel fails, before the intermediate node can determine which of the first working channel and the first protection channel fails, the second working channel and the first protection channel There is always one of the two protection channels that can receive normal signals. At the same time, after the intermediate node judges that the first working channel is normal and the first protection channel is faulty, the intermediate node sends the signal of the first working channel to the second working channel and the second protection channel; the intermediate node judges that the first working channel After a failure and the first protection channel is normal, the intermediate node sends the signal of the first protection channel to the second working channel and the second protection channel; it ensures that one of the first working channel and the first protection channel fails, and the intermediate node After the node judges the specific fault channel, through the signal selection of the intermediate node selection unit, the signals transmitted on the second working channel and the second protection channel are normal, thereby increasing the stability of the protection system, and the two nodes In the case of failure of one of the channels, the switching time is shortened.

The SNC/S monitoring method stipulated in the standard can be used between the first node and the intermediate node, and a monitoring sublayer is inserted on the connection between the first node and the intermediate node to check the quality of the connection signal between the first node and the intermediate node to monitor. Specifically, the first monitoring information is the sub-layer monitoring information corresponding to the first signal obtained by using the SNC/S monitoring method between the first node and the first working channel; the second monitoring information is obtained through the first node and the first working channel The sub-layer monitoring information corresponding to the second signal obtained by using the SNC/S monitoring method between a protection channel.

Similarly, the SNC/N monitoring specified in section 11.2.1.2 of ITU-T G.808.1 can be used between the first node and the intermediate node, by monitoring the quality of each signal before the processing unit, the monitoring method is in Signals are implemented by detecting end-to-end or sub-layer overhead information. The first monitoring information is the end-to-end or sub-layer overhead information corresponding to the first signal obtained by using the SNC/N monitoring method between the first node and the first working channel; the second monitoring information is through the first node The end-to-end or sub-layer overhead information corresponding to the second signal obtained by using the SNC/N monitoring manner between the first protection channel and the first protection channel.

Similarly, the SNC/I monitoring specified in Section 11.2.1.3 of ITU-T G.808.1 can also be used between the first node and the intermediate node. This monitoring method is used to protect a single link connection, that is to say, it only spans a section The plumbing of the service layer. In this way, the failure of the service layer can be used, and the service layer failure or degradation alarm can be derived from the adaptation function of the subnet connection SNC signal to be protected and the service layer. Based on this alarm, the processing unit can judge whether the signal is normal. The first monitoring information is the service layer monitoring information corresponding to the first signal obtained by using the SNC/I monitoring method between the first node and the first working channel; the second monitoring information is obtained by using the SNC/I monitoring method between the first node and the first protection channel The service layer monitoring information corresponding to the second signal obtained by using the SNC/I monitoring method during the period.

As shown in Figure 4, it is a cascaded protection system according to another embodiment of the present invention. The intermediate switching node in the figure is connected to the first node through the first working channel and the first protection channel, and is connected to the first node through the second working channel and the second protection channel. Connected to the second node, the receiving unit of the intermediate node includes a first subunit, a second subunit, and an intermediate crossover unit; the processing unit of the intermediate node includes a third subunit and a fourth subunit. in:

a first subunit, configured to receive a first signal of the first working channel and output the first signal;

a second subunit, configured to receive the second signal of the first protection channel and output the second signal;

an intermediate crossover unit, configured to receive and output the first signal output by the first subunit and the second signal output by the second subunit;

The third subunit is configured to receive the first signal and the second signal output by the intermediate cross unit, and receive the first monitoring information corresponding to the first signal and the second signal corresponding to The second monitoring information, judging whether the first signal and the second signal are normal based on the first monitoring information and the second monitoring information; when the first signal and the second signal are normal , output the first signal to the second working channel; when the first signal is normal and the second signal fails, output the first signal to the second working channel; when the When the first signal fails and the second signal is normal, output the second signal to the second working channel;

a fourth subunit, configured to receive the first signal and the second signal output by the intermediate cross unit, and receive the first monitoring information corresponding to the first signal and the monitoring information corresponding to the second signal The second monitoring information, judging whether the first signal and the second signal are normal based on the first monitoring information and the second monitoring information; when the first signal and the second signal are normal , output the second signal to the second protection channel; when the first signal is normal and the second signal fails, output the first signal to the second protection channel; when the When the first signal fails and the second signal is normal, the second signal is output to the second protection channel.

In the embodiment of FIG. 4, the first monitoring information corresponding to the first signal and the second monitoring information corresponding to the second signal are respectively received by the third subunit and the fourth subunit, through the first monitoring information and the second monitoring information The information judges whether the first signal and the second signal are normal. It is easy to understand that the third subunit can also receive the first monitoring information corresponding to the first signal and the second monitoring information corresponding to the second signal, and judge whether the first signal and the second signal are based on the first monitoring information and the second monitoring information. Normal, output the result to the fourth subunit. It is easy to understand that the fourth subunit can also receive the first monitoring information corresponding to the first signal and the second monitoring information corresponding to the second signal, and judge whether the first signal and the second signal are based on the first monitoring information and the second monitoring information. Normal, output the result to the third subunit.

The embodiment of the present invention also provides an intermediate node used in the above-mentioned cascade protection system, whose structure and function are the same as those of the intermediate node in the cascade protection system provided by the embodiment of the present invention. In one embodiment of the present invention, an intermediate node is provided, the intermediate node is connected to the first node through the first working channel and the first protection channel, and is connected to the second node through the second working channel and the second protection channel , the intermediate node includes a receiving unit and a processing unit, where:

The receiving unit outputs after receiving the first signal of the first working channel and the second signal of the first protection channel, and outputs after receiving the first monitoring information corresponding to the first signal and the second monitoring information corresponding to the second signal;

The processing unit judges whether the first signal and the second signal are normal according to the first monitoring information and the second monitoring information output by the receiving unit; if it is judged that the first signal and the second signal are normal, output the first signal to the second The working channel outputs the second signal to the second protection channel.

Since both the first working channel and the first protection channel are normal, the first signal of the first working channel is transmitted to the working channel of the second node, and the second signal of the first protection channel is transmitted to the protection channel of the second node , to ensure that after a node detects a fault, it will only send an AIS signal to one of the working channel and the protection channel between the node and the next node while performing the switchover, thereby preventing the working channel and the protection channel from receiving AIS at the same time The signal and the AIS signal of the working channel and the protection channel are asynchronously lost, which may cause repeated switching, which shortens the time for switching from the service when a single point of failure occurs.

In another embodiment of the present invention, an intermediate node is provided, the intermediate node is connected to the first node through the first working channel and the first protection channel, and is connected to the second node through the second working channel and the second protection channel connected, the intermediate node includes a receiving unit and a processing unit, wherein:

The receiving unit is used to receive the first signal of the first working channel and the second signal of the first protection channel and then output it, and receive the first monitoring information corresponding to the first signal and the second monitoring information corresponding to the second signal before outputting;

The processing unit is used to judge whether the first signal and the second signal are normal according to the first monitoring information and the second monitoring information output by the receiving unit; if it is judged that the first signal and the second signal are normal, output the first signal to the The second working channel outputs the second signal to the second protection channel. If it is judged that the first signal is normal and the second signal is faulty, output the first signal to the second working channel and the second protection channel; if it is judged that the second signal is normal but the first signal is faulty, output the second signal to the second working channel and second protection channel.

Fig. 5 is a flow chart of a cascade protection method provided by another embodiment of the present invention, which is used in a cascade protection system, the cascade protection system includes a first node, a second node and an intermediate node, and the intermediate The node is connected to the first node through the first working channel and the first protection channel, and is connected to the second node through the second working channel and the second protection channel. The specific steps are:

S501. The intermediate node receives a first signal on a first working channel and a second signal on a first protection channel, and receives first monitoring information corresponding to the first signal and second monitoring information corresponding to the second signal.

Wherein, the first monitoring information received by the intermediate node is the end-to-end or sub-layer overhead corresponding to the first signal obtained by using the SNC/N monitoring method between the first node and the first working channel; the first monitoring information received by the intermediate node The second monitoring information is the end-to-end or sub-layer overhead corresponding to the second signal obtained by using the SNC/N monitoring method between the first node and the first protection channel.

Or, the first monitoring information received by the intermediate node is the sub-layer monitoring information corresponding to the first signal obtained by adopting the SNC/S monitoring mode between the first node and the first working channel; the second monitoring information received by the intermediate node is The sub-layer monitoring information corresponding to the second signal obtained by using the SNC/S monitoring method between the first node and the first protection channel.

Or, the first monitoring information received by the intermediate node is the service layer monitoring information corresponding to the first signal obtained by adopting the SNC/I monitoring mode between the first node and the first working channel; the second monitoring information received by the intermediate node is The service layer monitoring information corresponding to the second signal obtained by using the SNC/I monitoring method between the first node and the first protection channel.

S502. Determine whether the input first signal and second signal are normal according to the first monitoring information and the second monitoring information.

S503. If all are normal, output the first signal to the second working channel, and output the second signal to the second protection channel.

Since both the first working channel and the first protection channel are normal, the first signal of the first working channel is transmitted to the working channel of the second node, and the second signal of the first protection channel is transmitted to the protection channel of the second node , to ensure that after a node detects a fault, it will only send an AIS signal to one of the working channel and the protection channel between the node and the next node while performing the switchover, thereby preventing the working channel and the protection channel from receiving AIS at the same time The signal and the AIS signal of the working channel and the protection channel are asynchronously lost, which may cause repeated switching, which shortens the time for switching from the service when a single point of failure occurs.

In addition to steps S501, S502, and S503, the cascade protection method provided by the embodiment of the present invention may also include:

S504. If the first signal is normal but the second signal is faulty, output the first signal to the second working channel and the second protection channel.

S505. If the first signal fails but the second signal is normal, output the second signal to the second working channel and the second protection channel.

Since both the first working channel and the first protection channel are normal, the first signal of the first working channel is transmitted to the working channel of the second node, and the second signal of the first protection channel is transmitted to the protection channel of the second node channel, which ensures that when one of the first working channel and the first protection channel fails, before the intermediate node can determine which of the first working channel and the first protection channel fails, the second working channel and the first protection channel There is always one of the two protection channels that can receive normal signals. At the same time, after the intermediate node judges that the first working channel is normal and the first protection channel is faulty, the intermediate node sends the signal of the first working channel to the second working channel and the second protection channel; the intermediate node judges that the first working channel After a failure and the first protection channel is normal, the intermediate node sends the signal of the first protection channel to the second working channel and the second protection channel; it ensures that one of the first working channel and the first protection channel fails, and the intermediate node After the node judges the specific fault channel, through the signal selection of the intermediate node selection unit, the signals transmitted on the second working channel and the second protection channel are normal, thereby increasing the stability of the protection system, and the two nodes In the case of failure of one of the channels, the switching time is shortened.

For those skilled in the art, the ideas of the embodiments of the present invention are applicable to SDH, ATM, ETH and other protections using similar technologies, and there will be changes in specific implementations. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims (7)

1. An intermediate node, connected to the first node through the first working channel and the first protection channel, and connected to the second node through the second working channel and the second protection channel, characterized in that the intermediate node comprises: a receiving unit, configured to receive the first signal of the first working channel and the second signal of the first protection channel and then output it, and receive the first monitoring information corresponding to the first signal and the first monitoring information corresponding to the second signal output after the second monitoring information; a processing unit, configured to judge whether the first signal and the second signal are normal according to the first monitoring information and the second monitoring information output by the receiving unit; If it is judged that both the first signal and the second signal are normal, output the first signal to the second working channel, and output the second signal to the second protection channel; outputting the first signal to the second working channel and the second protection channel if it is judged that the first signal is normal and the second signal is faulty; If it is determined that the second signal is normal and the first signal is faulty, the second signal is output to the second working channel and the second protection channel. 2. The intermediate node according to claim 1, wherein the receiving unit comprises: a first subunit, configured to receive the first signal of the first working channel and output the first signal; a second subunit, configured to receive the second signal of the first protection channel and output the second signal; an intermediate crossover unit, configured to receive and output the first signal output by the first subunit and the second signal output by the second subunit; The processing unit includes: The third subunit is configured to receive the first signal and the second signal output by the intermediate cross unit, and receive the first monitoring information corresponding to the first signal and the second signal corresponding to The second monitoring information, judging whether the first signal and the second signal are normal based on the first monitoring information and the second monitoring information; when the first signal and the second signal are normal , output the first signal to the second working channel; when the first signal is normal and the second signal fails, output the first signal to the second working channel; when the When the first signal fails and the second signal is normal, output the second signal to the second working channel; a fourth subunit, configured to receive the first signal and the second signal output by the intermediate cross unit, and receive the first monitoring information corresponding to the first signal and the monitoring information corresponding to the second signal The second monitoring information, judging whether the first signal and the second signal are normal based on the first monitoring information and the second monitoring information; when the first signal and the second signal are normal , output the second signal to the second protection channel; when the first signal is normal and the second signal fails, output the first signal to the second protection channel; when the When the first signal fails and the second signal is normal, the second signal is output to the second protection channel. 3. A cascade protection system, comprising a first node, an intermediate node and a second node, the intermediate node is connected to the first node through a first working channel and a first protection channel, and is connected to the first node through a second working channel and a second The second protection channel is connected to the second node, wherein the intermediate node includes: a receiving unit, configured to receive the first signal of the first working channel and the second signal of the first protection channel and then output it, and receive the first monitoring information corresponding to the first signal and the first monitoring information corresponding to the second signal output after the second monitoring information; a processing unit, configured to judge whether the first signal and the second signal output by the receiving unit are normal according to the first monitoring information and the second monitoring information output by the receiving unit; If it is judged that both the first signal and the second signal are normal, output the first signal to the second working channel, and output the second signal to the second protection channel; outputting the first signal to the second working channel and the second protection channel if it is judged that the first signal output by the receiving unit is normal and the second signal is faulty; If it is determined that the second signal output by the receiving unit is normal and the first signal is faulty, the second signal is output to the second working channel and the second protection channel. 4. A cascade protection method, used in a cascade protection system, the cascade protection system includes a first node, an intermediate node and a second node, and the intermediate node communicates with the first working channel and the first protection channel The first node is connected to the second node through the second working channel and the second protection channel, which is characterized in that it includes: The intermediate node receives the first signal on the first working channel and the second signal on the first protection channel, and receives the first monitoring information corresponding to the first signal and the second monitoring information corresponding to the second signal. surveillance information; judging whether the input first signal and second signal are normal based on the first monitoring information and the second monitoring information, If all are normal, output the first signal to the second working channel, and output the second signal to the second protection channel; If the first signal is normal and the second signal is faulty, output the first signal to the second working channel and the second protection channel; If the first signal fails and the second signal is normal, the second signal is output to the second working channel and the second protection channel. 5. The cascade protection method according to claim 4, characterized in that: The first monitoring information received by the intermediate node is obtained by using SNC/N monitoring between the first node and the first working channel, corresponding to the end-to-end or sub-layer of the first signal s expenses; The second monitoring information received by the intermediate node is obtained by using SNC/N monitoring between the first node and the first protection channel, corresponding to the end-to-end or sub-layer of the second signal s expenses. 6. The cascade protection method according to claim 4, characterized in that: The first monitoring information received by the intermediate node is sub-layer monitoring information corresponding to the first signal obtained by using SNC/S monitoring between the first node and the first working channel; The second monitoring information received by the intermediate node is sub-layer monitoring information corresponding to the second signal obtained by using SNC/S monitoring between the first node and the first protection channel. 7. The cascade protection method according to claim 4, characterized in that: The first monitoring information received by the intermediate node is service layer monitoring information corresponding to the first signal obtained by using SNC/I monitoring between the first node and the first working channel; The second monitoring information received by the intermediate node is service layer monitoring information corresponding to the second signal obtained by using SNC/I monitoring between the first node and the first protection channel.

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